P0300

Car is a '96 Z28, I just got the distributor back from MSD about 6 weeks ago (failed optical sensor) and put everything back together and everything was good.

I was out of town last week and when I came back the car stumbles and misfires like crazy, almost undriveable. At idle it will either idle at ~1700 or it will almost die and the IAC will constantly have to keep the motor alive.

Car shows P0300 which is random misfire and it briefly showed P0134 which is Oxygen 02 Sensor Circuit No Activity Detected (Bank I Sensor 1) (I cleared that and it hasn't come back, caused by the severe misfire maybe?). I haven't been driving the car much so no clue if P0134 will come back.

Any clues? It would be a big PITA to have to pull the distributor again, it has worked perfectly since I put it back in. This isn't a small miss at speed or anything, its bad enough that the car isn't really driveable.

I haven't pulled any plugs but they are relatively new, as are the plug wires and I just replaced the fuel filter.